JP5119370B1 - Biogas injection facility for city gas pipeline - Google Patents

Abstract

An object of the present invention is to provide a biogas injection facility for a city gas conduit having a configuration that makes it easy to adjust the amount of heat and odor concentration of purified gas.
[MEANS FOR SOLVING PROBLEMS] A trace component removing device (91) that removes at least carbon dioxide remaining in a purified gas obtained by purifying digestion gas, and LPG is injected into the purified gas that has passed through the trace component removing device (91). Is a biogas injection facility 100 for a city gas conduit comprising a calorific value adjusting device 92 for adjusting the amount of heat and an odorizing device 23 for adding an odorant to the purified gas into which LPG has been injected. Gas flowing in the purified gas pipe 70 between the trace component removing device 91 and the position P where LPG is injected, based on the gas flow meter 24 and the flow signal from the gas flow meter 24. A purified gas pipe flow rate adjustment valve 25 for adjusting the flow rate is provided.
[Selection] Figure 1

Description

  The present invention relates to a biogas injection facility for a city gas conduit.

  Biogas refers to gas generated by fermentation and anaerobic digestion of biological waste, organic fertilizer, biodegradable substances, sewage, garbage, etc. (the main component is methane). Moreover, city gas means the gas for fuel which has methane as a main component (it uses natural gas as a raw material).

  Here, biogas obtained by methane fermentation of biomass such as organic waste such as sewage sludge and garbage and organic wastewater such as food factory effluent is attracting attention as a new energy. The biogas obtained by the methane fermentation treatment is usually called “digestion gas”, and the components in the digestion gas are about 60% by volume of methane and about 40% by volume of carbon dioxide. In recent years, it has been awaited that this digested gas is purified and the purified gas obtained is supplied to each household like city gas, that is, the purified digested gas is used as city gas. .

  As a technique for purifying digestion gas and using it as city gas, for example, there is one described in Patent Document 1. Patent Document 1 describes a technique effective for removing oxygen remaining in methane gas obtained by purifying digestion gas.

JP 2010-229248 A

  On the other hand, in order to use purified digestion gas (purified gas) as city gas, it is necessary to adjust the calorific value, odor concentration, etc. of the purified gas within the range required (specified) as city gas. In addition, when supplying purified gas to an existing city gas conduit, it is necessary to be able to adjust the supply amount (flow rate) of the purified gas because the amount of digestion gas generated varies.

  For the purpose of adjusting the supply amount (flow rate) of purified gas to the city gas conduit, a flow rate adjustment valve is provided in the purified gas tube section immediately before the position where it is connected to the city gas conduit so that the gas flow rate can be adjusted. It is considered reasonable to keep it.

  However, if the flow rate of the purified gas is low at the injection point of the high calorie gas for adjusting the calorie of the purified gas, the present inventors are within the range where the amount of heat of the purified gas is required (specified) as city gas. I found it difficult to adjust. If the flow rate of the purified gas is low at the injection point of the odorant for adjusting the odor concentration of the purified gas, the odor concentration of the purified gas is adjusted within the range required (specified) as city gas. I found it difficult.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a biogas injection facility for a city gas conduit having a configuration that makes it easy to adjust the calorific value and odor concentration of purified gas. That is.

  The present invention provides a trace component removing device that removes at least carbon dioxide remaining in a purified gas obtained by removing carbon dioxide and sulfur impurities contained in biogas, and the purified gas that has passed through the trace component removing device. A calorie adjusting device for injecting a high calorie gas having a larger calorie than methane gas to adjust the calorie of the refined gas, an odorant device for adding an odorant to the refined gas into which the high calorie gas is injected, A biogas injection facility for a city gas conduit comprising a gas flow meter, and a gas flow meter, and a purified gas pipe section between the trace component removal device and the position where the high-calorie gas is injected A purified gas pipe flow rate adjusting valve is provided for adjusting the flow rate of the gas flowing through the purified gas pipe unit based on the flow rate signal of the.

  According to the present invention, the flow rate of the purified gas is stabilized at the injection point of the high-calorie gas, and as a result, the amount of heat and the odor concentration of the purified gas can be easily adjusted.

It is a block diagram which shows the biogas injection equipment to the city gas conduit | pipe which concerns on one Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following explanation, digestion gas (biogas) obtained by subjecting sewage sludge to methane fermentation is a purification target for supplying the city gas conduit. However, the present invention provides methane fermentation of sewage sludge. It can also be applied to biogas other than the resulting digestion gas.

(Configuration of biogas injection equipment)
As shown in FIG. 1, the digestion gas generated in the digestion tank 1 is sent to the biogas purification device 2, and carbon dioxide and sulfur impurities contained in the digestion gas are removed by the biogas purification device 2. The purified gas obtained by removing carbon dioxide and sulfur impurities is stored in the intermediate pressure gas holder 3. Thereafter, the purified gas is supplied to the city gas conduit 28 through which the city gas flows through the biogas injection facility 100 (the biogas injection facility to the city gas conduit).

(Digestion tank)
Concentrated sludge generated by treating sewage from a sewage treatment facility (not shown) is sent to the digestion tank 1. The digestion tank 1 is used for anaerobically digesting the charged concentrated sludge, thereby generating digestion gas. The main components of the digestion gas are methane and carbon dioxide, with methane being about 60% by volume and carbon dioxide being about 40% by volume.

(Biogas purification equipment)
The biogas purification apparatus 2 is an apparatus for purifying digestion gas by removing carbon dioxide and sulfur-based impurities (for example, H ₂ S) contained in the digestion gas. For example, by bringing the digestion gas into contact with water, carbon dioxide and sulfur-based impurities contained in the digestion gas are dissolved in water, and carbon dioxide and sulfur-based impurities are separated and removed from the digestion gas. In the sewage treatment plant, for example, sand filtration water is used as digestion gas purification water.

(Medium pressure gas holder)
The medium pressure gas holder 3 is a tank for temporarily storing purified gas obtained by purifying digestion gas in the biogas purification device 2. The pressure in the intermediate pressure gas holder 3 is measured by the pressure gauge 4 and is set to a pressure in the range of 0.4 MPa to 1.0 MPa, for example.

(Biogas injection equipment)
The main devices constituting the biogas injection facility 100 are a trace component removing device 91, a calorific value adjusting device 92, and an odorizing device 23. The intermediate pressure gas holder 3 and the city gas conduit 28 are connected by a purified gas pipe 70. A purified gas pipe 71 is branched from the purified gas pipe 70 between the intermediate pressure gas holder 3 and the trace component removing device 91. The purified gas pipe 71 is a transfer pipe for using the purified gas for other purposes. Other uses include, for example, fuel gas for natural gas automobiles, fuel gas for hot water boilers that constitute digestion equipment among sewage treatment equipment, and the like.

(Trace component removal equipment)
The trace component removal device 91 is a device for removing oxygen and carbon dioxide remaining in the purified gas purified by the biogas purification device 2. Note that the oxygen concentration required (specified) as city gas is, for example, 0.01% by volume or less, and the carbon dioxide concentration is, for example, 0.5% by volume or less.

  The main components for removing oxygen remaining in the purified gas in the trace component removing device 91 are a water electrolysis high-purity hydrogen oxygen generator 13 which is a water electrolysis device as a hydrogen supply means, a hydrogen flow rate control device 15, An oxygen removal catalyst tower 20. The oxygen removal catalyst tower 20 is filled with, for example, palladium (Pd).

  A gas flow meter 11 is provided in the purified gas pipe 70 portion between the pressure gauge 4 and the oxygen removal catalyst tower 20, and flows through the purified gas pipe 70 portion between the gas flow meter 11 and a position where hydrogen is injected. The oxygen concentration of the purified gas is measured by the oxygen concentration meter 12. A hydrogen supply pipe for injecting hydrogen generated by the water electrolysis type high purity hydrogen oxygen generation 13 into the purified gas pipe 70 is provided with a hydrogen flow meter 14 and a hydrogen flow control valve 16.

  A gas cooler 21 and a dehumidifier 22 are provided in the purified gas pipe 70 on the downstream side of the oxygen removal catalyst tower 20. In the sewage treatment plant, for example, sand filtered water is supplied to the gas cooler 21 as cooling water.

  Here, the hydrogen flow control device 15 measures the oxygen concentration of the purified gas flowing through the gas flow meter 11, the oxygen concentration meter 12, the hydrogen flow meter 14, and the purified gas pipe 70 on the downstream side of the odorizing device 23. A signal from the oximeter 40 is input. The hydrogen flow rate control device 15 obtains a necessary hydrogen amount based on these signals, and controls the hydrogen flow rate adjustment valve 16 to adjust the hydrogen amount injected into the purified gas pipe 70.

  Hydrogen injected into the purified gas pipe 70 and oxygen remaining in the purified gas undergo a catalytic reaction in the oxygen removal catalyst tower 20 to become water. The heat of catalytic reaction is removed by the gas cooler 21, and water (water) generated by the catalytic reaction is removed by the dehumidifier 22.

  Next, a carbon dioxide remover 10 is provided in the purified gas pipe 70 between the oxygen removal catalyst tower 20 and the gas cooler 21. The carbon dioxide remover 10 includes at least two adsorbing towers arranged in parallel and filled with an adsorbent. Here, about the carbon dioxide remover 10 provided with two adsorption towers, the removal operation of the carbon dioxide adsorbed by the adsorbent will be described. When removing the adsorbed carbon dioxide, the inlet and outlet valves of the removing adsorption tower are closed, and the inside of the adsorption tower is evacuated to remove the carbon dioxide. At this time, the purified gas is flowing through the other adsorption tower arranged in parallel. When the removal of carbon dioxide is completed, the pressure in the two adsorption towers is returned to a constant value (pressure equalization step), and then the adsorption of carbon dioxide is resumed. Since the purified gas continues to flow through the carbon dioxide remover 10, the carbon dioxide adsorbed by the adsorbents in the two adsorption towers cannot be removed at the same time, and thus the carbon dioxide is removed by switching the adsorption towers. The means for removing carbon dioxide remaining in the purified gas is not limited to the carbon dioxide remover 10 of a type including at least two adsorbing towers arranged in parallel and filled with an adsorbent.

(Heat quantity adjustment device)
The calorific value adjusting device 92 is a device for adjusting the calorific value of the refined gas by injecting LPG, which is a high calorie gas having a larger calorie than methane gas, into the refined gas that has passed through the trace component removing device 91. Note that the high-calorie gas injected into the purified gas is not limited to LPG.

  The calorific value adjustment device 92 includes an LPG supply device 30 and an LPG flow rate control device 32. An LPG flow meter 31 and an LPG flow rate adjustment valve 33 are provided in an LPG supply pipe for injecting LPG into the purified gas pipe 70. The LPG injection point P (injection position) into the purified gas pipe 70 is the purified gas pipe 70 portion on the downstream side of the trace component removing device 91.

  Here, signals from the LPG flow meter 31 and a gas flow meter 24 described later are input to the LPG flow control device 32. The LPG flow rate control device 32 obtains a necessary LPG amount based on these signals, and controls the LPG flow rate adjustment valve 33 to adjust the LPG amount injected into the purified gas pipe 70.

(Odoring device)
The odorizing device 23 is a device for adding an odorant (TBM + DMS) to the purified gas into which LPG has been injected. The odorizing device 23 is provided in 70 parts of the purified gas pipe downstream of the LPG injection point P.
(Gas flow meter and purified gas pipe flow control valve)
Here, in the purified gas pipe 70 part between the trace component removing device 91 and the LPG injection point P, a gas flow meter 24 for measuring the flow rate of the purified gas flowing through the purified gas pipe 70 part, and the gas flow meter 24 A purified gas pipe flow rate adjustment valve 25 for adjusting the flow rate of the gas flowing through the purified gas pipe 70 based on the flow rate signal is provided. More specifically, in this embodiment, a gas flow meter 24 and a purified gas pipe flow rate adjustment valve 25 are provided in the purified gas pipe 70 portion between the dehumidifier 22 and the LPG injection point P.

  Further, the gas flow meter 24 is provided between the purified gas pipe flow rate adjustment valve 25 and the LPG injection point P.

  It should be noted that the distance between the purified gas pipe flow rate adjustment valve 25 and the gas flow meter 24 is preferably as small as possible without affecting the measured value of the gas flow meter 24. That is, it is preferable to provide the purified gas pipe flow rate adjustment valve 25 in the immediate vicinity of the gas flow meter 24 as long as the measurement value of the gas flow meter 24 is not affected. Further, the purified gas pipe flow rate adjustment valve 25 is set to the LPG injection point P side from the middle between the dehumidifier 22 (trace component removing device 91) and the LPG injection point P, and further to the measured value of the gas flow meter 24. It is preferably provided as close as possible to the LPG injection point P within a range where there is no influence.

  The order of the purified gas pipe flow rate adjustment valve 25 and the gas flow meter 24 may be reversed. That is, the gas flow meter 24 may be provided between the dehumidifier 22 which is a device constituting the trace component removing device 91 and the purified gas pipe flow rate adjustment valve 25.

  The purified gas pipe flow rate adjustment valve 25 may be an air operated valve or an electric valve (the same applies to other adjustment valves).

Signals from the pressure gauge 4 and the gas flow meter 24 are input to the purified gas flow control device 60. The purified gas flow control device 60 controls the purified gas pipe flow rate adjustment valve 25 based on these signals to adjust the gas flow rate so that the flow rate of the purified gas flowing through the purified gas pipe 70 becomes a predetermined value. Note that the gas flow rate may be adjusted by controlling the purified gas pipe flow rate adjusting valve 25 based on only the signal from the gas flow meter 24 without using the signal from the pressure gauge 4. The adjustment range of the flow rate of the purified gas is, for example, 27 to 167 Nm ³ / hr.

(Other equipment composing biogas injection equipment)
In addition to the above-described devices, the biogas injection facility 100 is provided with an analyzer 41, shut-off valves 26 and 50, a pressure reducing valve 27, and a gas combustion device 52.

(Action / Effect)
Since the amount of digestion gas (biogas) generated varies, the flow rate of the purified gas obtained by purifying it varies. Further, the flow rate of the purified gas used as the city gas also varies depending on the amount of the purified gas used for purposes other than the city gas. By temporarily storing the purified gas in the medium pressure gas holder 3, fluctuations in the flow rate of the purified gas can be suppressed to some extent, but this is not sufficient. Further, as described above, the carbon dioxide remover 10 includes adsorption tower switching, a pressure equalization step, and the like, and the flow rate of the purified gas flowing through the purified gas pipe 70 also varies depending on these.

  On the other hand, in order to use purified gas as city gas, it is necessary to adjust the amount of heat of purified gas within the range required (specified) as city gas, but high calories for adjusting the amount of heat of purified gas. If the flow rate of the purified gas is low at the gas injection point, it is difficult to adjust the amount of heat of the purified gas within the range required (defined) as city gas. If the flow rate of the purified gas is low at the injection point of the odorant for adjusting the odor concentration of the purified gas, the odor concentration of the purified gas is adjusted within the range required (specified) as city gas. It is difficult.

  However, a gas flow meter 24 and a purified gas pipe flow rate adjustment valve 25 are provided in the purified gas pipe 70 part between the trace component removing device 91 and the injection point P into which the high calorie gas is injected. By adjusting the flow rate of the purified gas by the purified gas pipe flow rate adjustment valve 25 based on the flow rate signal, the flow rate of the purified gas at the injection point P is more stable than the conventional one (variation is reduced). As a result, the heat quantity of the purified gas can be easily adjusted. Moreover, since the odorizing device 23 is provided on the downstream side of the injection point P, the flow of the purified gas at the injection point P is more stable than before, so that the odorizing device 23 is located on the downstream side. The flow rate of the purified gas at the agent injection point is also more stable than before, and the odor concentration of the purified gas can be easily adjusted.

  Further, by providing the gas flow meter 24 between the purified gas pipe flow rate adjustment valve 25 and the LPG injection point P, that is, on the secondary side (downstream side) of the purified gas pipe flow rate adjustment valve 25, it is closer to the injection point P. The flow rate of the purified gas is adjusted based on the gas flow rate at the position, and the flow rate of the purified gas at the injection point P becomes more stable.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

1: Digestion tank 2: Biogas purification device 3: Medium pressure gas holder 23: Odor device 24: Gas flow meter 25: Purified gas pipe flow rate adjustment valve 28: City gas pipe 70: Purified gas pipe 91: Trace component removal device 92: Calorific value adjustment device 100: Biogas injection equipment P: City gas conduit P: Position where LPG (high calorie gas) is injected

Claims (2)

A trace component removing device that removes at least carbon dioxide remaining in purified gas obtained by removing carbon dioxide and sulfur-based impurities contained in biogas;
A calorific value adjusting device that adjusts the calorific value of the purified gas by injecting a high calorie gas having a calorific value larger than that of methane gas into the purified gas that has passed through the trace component removing device;
An odorizing device for adding an odorant to the purified gas into which the high-calorie gas has been injected;
In a biogas injection facility into a city gas conduit comprising:
Gas flow rate that flows through the purified gas pipe unit based on the flow rate signal from the gas flow meter and the gas flow meter to the purified gas pipe unit between the trace component removing device and the position where the high calorie gas is injected the purified gas pipe flow rate adjusting valve for adjusting is provided a
The purified gas pipe flow rate adjustment valve is provided on the position side where the high calorie gas is injected, rather than the middle between the trace component removing device and the position where the high calorie gas is injected. A biogas injection facility for city gas conduits. The biogas injection facility for a city gas conduit according to claim 1,
The gas flow meter is provided between the purified gas pipe flow rate adjustment valve and a position where the high calorie gas is injected, and the biogas injection equipment to the city gas conduit is characterized by the above.

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